Method and apparatus for transmitting uplink signal in wireless communication system

ABSTRACT

A method for transmitting an uplink signal at a UE in a wireless communication system includes, when a virtual cell ID for a reference signal for demodulation of a physical uplink channel is provided, generating a sequence of the reference signal on the basis of the virtual cell ID, and transmitting the generated reference signal to an eNB. A sequence hopping pattern of the reference signal can be determined on the basis of the virtual cell ID.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/376,829, filed on Aug. 5, 2014, now U.S. Pat. No. 9,401,790, which isthe National Stage filing under 35 U.S.C. 371 of InternationalApplication No. PCT/KR2013/001322, filed on Feb. 20, 2013, which claimsthe benefit of U.S. Provisional Application No. 61/600,999, filed onFeb. 20, 2012, 61/602,587, filed on Feb. 23, 2012 and 61/619,408, filedon Apr. 2, 2012, the contents of which are all hereby incorporated byreference herein in their entirety.

TECHNICAL FIELD

The present description relates to wireless communication, and morespecifically, to a method and apparatus for transmitting an uplinksignal.

BACKGROUND ART

To satisfy increasing data throughput in a wireless communicationsystem, MIMO, multi-base station cooperation technology, etc. forincreasing throughput of data transmitted in a limited frequency bandhave been developed.

An enhanced wireless communication system that supports multi-basestation cooperative communication through which a plurality of eNBscommunicate with user equipments (UEs) using the same time-frequencyresource can provide increased data throughput, compared to aconventional wireless communication system in which one eNB communicateswith UEs. eNBs participating in cooperative communication may bereferred to as cells, antenna ports, antenna port groups, RRHs (RemoteRadio Heads), transport points, reception points, access points, etc.

DISCLOSURE Technical Problem

With the introduction of new wireless communication technology, thenumber of UEs to which an eNB needs to provide a service in apredetermined resource region increases and the quantity of data andcontrol information transmitted/received between the eNBs and UEs towhich the eNB provides the service also increases. Since the quantity ofradio resource that can be used for the eNB to communicate with the UEsis finite, there is a need for a new method by which the ENB efficientlytransmits/receives uplink/downlink data and/or uplink/downlink controlinformation to/from UEs using finite radio resource.

An object of the present invention devised to solve the problem lies ona new method for transmitting an uplink reference signal to supportenhanced uplink transmission and a method for successfully receiving theuplink reference signal at an uplink signal receiver.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting an uplink signal at a user equipment (UE) in awireless communication system, the method including, when a virtual cellID n_(ID) ^(PUSCH) for a reference signal for demodulation of a physicaluplink shared channel (PUSCH) is provided, generating a sequence of thereference signal on the basis of n_(ID) ^(PUSCH), and transmitting thegenerated reference signal to an eNB. A pseudo-random sequence generatorused to determine sequence hopping of the reference signal may beinitialized according to

$c_{init} = {{\left\lfloor \frac{n_{ID}^{PUSCH}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$at the start of each radio frame, c_(init) may be an initial value of apseudo-random sequence and f_(ss) ^(PUSCH) may be a sequence shiftpattern of the reference signal.

In another aspect of the present invention, provided herein is a UEdevice for transmitting an uplink signal, including a receiver, atransmitter, and a processor, wherein, when a virtual cell ID n_(ID)^(PUSCH) for a reference signal for demodulation of a PUSCH is provided,the processor is configured to generate a sequence of the referencesignal on the basis of n_(ID) ^(PUSCH) and to transmit the generatedreference signal to an eNB. A pseudo-random sequence generator used todetermine sequence hopping of the reference signal may be initializedaccording to

$c_{init} = {{\left\lfloor \frac{n_{ID}^{PUSCH}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$at the start of each radio frame, c_(init) may be an initial value of apseudo-random sequence and f_(ss) ^(PUSCH) may be a sequence shiftpattern of the reference signal.

The following may be commonly applied to the above-described embodimentsof the present invention.

f_(ss) ^(PUSCH) may be determined according to f_(ss) ^(PUSCH)=n_(ID)^(PUSCH) mod 30 and mod may denote a modulo operation.

Sequence hopping may be applied when sequence group hopping for thereference signal is disabled.

Sequence hopping may be applied when the length of the reference signalis M_(sc) ^(RS)≧6N_(sc) ^(RB), M_(sc) ^(RS) may denote the length of thereference signal and may be defined as M_(sc) ^(RS)=m·N_(sc) ^(RB),1≦m≦N_(RB) ^(max,UL), N_(RB) ^(max,UL) may represent a maximum uplinkbandwidth configuration and may be expressed by an integer multiple ofN_(sc) ^(RB), and N_(sc) ^(RB) be a resource block size and may berepresented by the number of subcarriers.

The number v of a base sequence of the reference signal may bedetermined according to the sequence hopping.

When a value of n_(ID) ^(PUCCH) is not provided, c_(init) may bedetermined according to

${c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}},$and N_(ID) ^(cell) may be a physical layer cell ID.

When a value of n_(ID) ^(PUSCH) is not provided, f_(ss) ^(PUSCH) may bedetermined according to f_(ss) ^(PUSCH)=(N_(ID) ^(cell)+Δ_(ss))mod 30,Δ_(ss) may be set by a higher layer and Δ_(ss)ε{0, 1, . . . , 29}.

n_(ID) ^(PUSCH) may be provided by a higher layer.

n_(ID) ^(PUSCH) may be set to one of 0 to 509.

n_(ID) ^(PUSCH) may be set to a value making a base sequence of thereference signal for the UE identical to a base sequence for other UEwhich MU-MIMO (Multi-User-Multiple Input Multiple Output)-paired withthe UE.

The reference signal may be transmitted on one SC-FDMA (Single CarrierFrequency Division Multiple Access) symbol in a slot in which the PUSCHis transmitted.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Advantageous Effects

The present invention can provide a new method for transmitting anuplink reference signal to support enhanced uplink transmission and amethod for successfully receiving the uplink reference signal at anuplink signal receiver.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIGS. 1A and 1B illustrate a radio frame structure;

FIG. 2 illustrates a resource grid;

FIG. 3 illustrates a downlink subframe structure;

FIG. 4 illustrates an uplink subframe structure;

FIG. 5 illustrates a downlink reference signal;

FIGS. 6 to 10 illustrate UCI transmission using PUCCH (Physical UplinkControl Channel) format 1 series, PUCCH format 2 series and PUCCH format3 series;

FIG. 11 illustrates multiplexing of uplink control information anduplink data in a PUSCH (Physical Uplink Shared Channel) region;

FIG. 12 illustrates an exemplary UL CoMP operation;

FIG. 13 is a flowchart illustrating an uplink reference signaltransmission method according to an embodiment of the present invention;and

FIG. 14 shows configurations of an eNB and a UE according to anembodiment of the present invention.

BEST MODE

Embodiments described hereinbelow are combinations of elements andfeatures of the present invention. The elements or features may beconsidered selective unless otherwise mentioned. Each element or featuremay be practiced without being combined with other elements or features.Further, an embodiment of the present invention may be constructed bycombining parts of the elements and/or features. Operation ordersdescribed in embodiments of the present invention may be rearranged.Some constructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between abase station (BS) and a User Equipment (UE). The BS is a terminal nodeof a network, which communicates directly with a UE. In some cases, aspecific operation described as performed by the BS may be performed byan upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘UE’ may be replaced with the term ‘terminal’,‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’, ‘SubscriberStation (SS)’, etc.

Specific terms used for the embodiments of the present invention areprovided to aid in understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3^(rd)Generation Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunication System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN-OFDMA Reference System) and theIEEE 802.16m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE/LTE-A system. However, thetechnical features of the present invention are not limited thereto.

A radio frame structure of 3GPP LTE is described with reference to FIG.1.

In a cellular orthogonal frequency division multiplex (OFDM) wirelesspacket communication system, uplink/downlink data packet transmission isperformed on a subframe basis and a subframe is defined as apredetermined time period including a plurality of OFDM symbols. 3GPPLTE supports a type 1 radio frame structure applicable to frequencydivision duplex (FDD) and a type 2 radio frame structure applicable totime division duplex (TDD).

FIG. 1A illustrates the type 1 radio frame structure. A radio frame isdivided into 10 subframes. Each subframe is further divided into twoslots in the time domain. A unit time during which one subframe istransmitted is defined as a transmission time interval (TTI). Forexample, one subframe may be 1 ms in duration and one slot may be 0.5 msin duration. A slot may include a plurality of OFDM symbols in the timedomain and a plurality of resource blocks in the frequency domain.Because 3GPP LTE adopts OFDMA for downlink, an OFDM symbol representsone symbol period. An OFDM symbol may be referred to as an SC-FDMAsymbol or symbol period. A resource block (RB) is a resource allocationunit including a plurality of contiguous subcarriers in a slot.

The number of OFDM symbols included in one slot may be changed accordingto the configuration of a cyclic prefix (CP). The CP includes anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be seven. If the OFDM symbols are configured by the extendedCP, since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is less than that of the case of the normalCP. In case of the extended CP, for example, the number of OFDM symbolsincluded in one slot may be six. If the channel state is unstable, forexample, if a UE moves at a high speed, the extended CP may be used inorder to further reduce interference between symbols.

FIG. 1B illustrates the type 2 radio frame structure. The type 2 radioframe includes two half-frames, each of which is made up of fivesubframes, a downlink pilot time slot (DwPTS), a guard period (GP), andan uplink pilot time slot (UpPTS), in which one subframe consists of twoslots. DwPTS is used to perform initial cell search, synchronization, orchannel estimation. UpPTS is used to perform channel estimation of abase station and uplink transmission synchronization of a UE. The guardinterval (GP) is located between an uplink and a downlink so as toremove interference generated in the uplink due to multi-path delay of adownlink signal. One subframe is composed of two slots irrespective ofthe radio frame type.

The radio frame structure is purely exemplary and thus the number ofsubframes in a radio frame, the number of slots in a subframe, or thenumber of symbols in a slot may vary.

FIG. 2 illustrates a resource grid in a downlink slot. A downlink slotincludes 7 OFDM symbols in the time domain and an RB includes 12subcarriers in the frequency domain, which does not limit the scope andspirit of the present invention. For example, a downlink slot includes 7OFDM symbols in case of a normal CP, whereas a downlink slot includes 6OFDM symbols in case of an extended CP. Each element of the resourcegrid is referred to as a resource element (RE). An RB includes 12×7 REs.The number of RBs in a downlink slot, N^(DL) depends on a downlinktransmission bandwidth. An uplink slot may have the same structure as adownlink slot.

Downlink Subframe Structure

FIG. 3 illustrates a downlink subframe structure. Up to three OFDMsymbols at the start of the first slot in a downlink subframe correspondto a control region to which control channels are allocated and theother OFDM symbols of the downlink subframe correspond to a data regionto which a physical downlink shared channel (PDSCH) is allocated.Downlink control channels used in 3GPP LTE include a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), and a physical hybrid automatic repeat request (HARQ) indicatorchannel (PHICH). The PCFICH is located in the first OFDM symbol of asubframe, carrying information about the number of OFDM symbols used fortransmission of control channels in the subframe. The PHICH delivers anHARQ acknowledgment/negative acknowledgment (ACK/NACK) signal inresponse to an uplink transmission. Control information carried on thePDCCH is called downlink control information (DCI). The DCI transportsuplink or downlink scheduling information, or uplink transmission powercontrol commands for UE groups. The PDCCH delivers information aboutresource allocation and a transport format for a downlink shared channel(DL-SCH), resource allocation information about an uplink shared channel(UL-SCH), paging information of a paging channel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a random access responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, transmission power controlinformation, voice over Internet protocol (VoIP) activation information,etc. A plurality of PDCCHs may be transmitted in the control region. AUE may monitor a plurality of PDCCHs. A PDCCH is formed by aggregationof one or more consecutive control channel elements (CCEs). A CCE is alogical allocation unit used to provide a PDCCH at a coding rate basedon the state of a radio channel. A CCE includes a set of REs. The formatof a PDCCH and the number of available bits for the PDCCH are determinedaccording to the correlation between the number of CCEs and a codingrate provided by the CCEs. An eNB determines the PDCCH format accordingto DCI transmitted to a UE and adds a cyclic redundancy check (CRC) tocontrol information. The CRC is masked by an identifier known as a radionetwork temporary identifier (RNTI) according to the owner or usage ofthe PDCCH. If the PDCCH is directed to a specific UE, its CRC may bemasked by a cell-RNTI (C-RNTI) of the UE. If the PDCCH carries a pagingmessage, the CRC of the PDCCH may be masked by a paging indicatoridentifier (P-RNTI). If the PDCCH carries system information,particularly, a system information block (SIB), its CRC may be masked bya system information ID and a System Information RNTI (SI-RNTI). Toindicate that the PDCCH carries a random access response in response toa random access preamble transmitted by a UE, its CRC may be masked by arandom access-RNTI (RA-RNTI).

Downlink Reference Signal

When a packet is transmitted in a wireless communication system, signaldistortion may occur during transmission because the packet istransmitted through a radio channel. To successfully receive a distortedsignal at a receiver, it is necessary to correct distortion of thereceived signal using channel information. To detect the channelinformation, a method of transmitting a signal known to a transmitterand the receiver and detecting the channel information using a degree ofdistortion when the signal is received through the channel is widelyused. The signal is called a pilot signal or a reference signal.

In transmission and reception of data using multiple antennas, thereceiver needs to know channel states between transmit antennas andreceive antennas to successfully receive a signal. Accordingly, aseparate reference signal is needed for each transmit antenna.

Downlink reference signals include a common reference signal (CRS)shared by all UEs in a cell and a dedicated reference signal (DRS) foronly a specific UE. Information for channel estimation and demodulationcan be provided according to these reference signals. The CRS is used toestimate a channel of a physical antenna, can be commonly received byall UEs in a cell, and is distributed in the overall band. The CRS canbe used for acquisition of channel state information (CSI) and datademodulation.

A receiver (UE) can estimate a channel state from the CRS and feed backindicators regarding channel quality, such as a channel qualityindicator (CQI), a precoding matrix index (PMI) and/or a rank indicator(RI), to a transmitter (eNB). The CRS may be called a cell-specificreference signal.

The DRS can be transmitted through a corresponding RE when demodulationof data on a PDSCH is needed. The UE may receive information aboutpresence or absence of a DRS from a higher layer and receive informationrepresenting that the DRS is valid only when a corresponding PDSCH ismapped. The DRS may also be called a UE-specific reference signal ormodulation reference signal (DMRS). The DRS (or UE-specific referencesignal) is used for data demodulation. A precoding weight used for aspecific UE is used for the DRS during multi-antenna transmission suchthat an equivalent channel corresponding a combination of a precodingweight transmitted through each transmit antenna and a transmissionchannel can be estimated when the UE receives the DRS.

FIG. 4 illustrates a pattern of matching a CRS and a DRS defined in 3GPPLTE to a downlink RB pair. A downlink RB pair as a unit to which areference signal is mapped can be represented by a product of onesubframe in the time domain and 12 subcarriers in the frequency domain.That is, one RB pair has a length corresponding to 14 OFDM symbols incase of normal CP and a length corresponding to 12 OFDM symbols in caseof extended CP. FIG. 4 shows an RB pair in case of normal CP.

FIG. 4 shows positions of reference signals on an RB pair in a system inwhich an eNB supports four transmit antennas. In FIG. 4, REs denoted by‘R0’, ‘R1’, ‘R2’ and ‘R3’ correspond to CRS positions for antenna portindexes 0, 1, 2 and 3. REs denoted by ‘D’ correspond to DRS positions.

High-order MIMO (Multiple Input Multiple Output), multi-celltransmission, enhanced multi-user (MU)-MIMO, etc. are considered inLTE-A evolved from 3GPP LTE. To efficiently operate reference signalsand support enhanced transmission schemes, DRS based data demodulationis being considered. That is, a DRS (or UE-specific reference signal orDMRS) for two or more layers can be defined to support data transmissionthrough an additional antenna, separately from a DRS (corresponding toantenna port index 5) for rank 1 beamforming defined in 3GPP LTE (e.g.release-8). For example, UE-specific reference signal ports supportingup to 8 transmit antenna ports can be defined as antenna port numbers 7to 12 and can be transmitted in REs which do not overlap with otherreference signals.

Furthermore, LTE-A may separately define an RS related to feedback ofchannel state information (CSI) such as CQI/PMI/RI for a new antennaport as a CSI-RS. For example, CSI-RS ports supporting up to 8 transmitantenna ports can be defined as antenna port numbers 15 to 22 and can betransmitted in REs which do not overlap with other reference signals.

Uplink Subframe Structure

FIG. 5 illustrates an uplink subframe structure.

Referring to FIG. 5, an uplink subframe may be divided into a controlregion and a data region in the frequency domain. One or more PhysicalUplink Control Channels (PUCCHs) carrying uplink control information maybe allocated to the control region and one or more Physical UplinkShared Channels (PUSCHs) carrying user data may be allocated to the dataregion.

Subcarriers far from a direct current (DC) subcarrier are used for thecontrol region in the UL subframe. In other words, subcarriers at bothends of an uplink transmission bandwidth are allocated for transmissionof uplink control information. The DC subcarrier is a component that isspared from signal transmission and mapped to carrier frequency f₀during frequency upconversion. A PUCCH from one UE is allocated to an RBpair in a subframe and the RBs of the RB pair occupy differentsubcarriers in two slots. This PUCCH allocation is called frequencyhopping of an RB pair allocated to a PUCCH over a slot boundary.However, if frequency hopping is not applied, the RB pair occupies thesame subcarriers.

A PUCCH may be used to transmit the following control information.

SR (Scheduling Request): used to request UL-SCH resource. Thisinformation is transmitted using OOK (On-Off Keying).

HARQ-ACK: response to a PDCCH and/or a response to a downlink datapacket (e.g. codeword) on a PDSCH. This information represents whetherthe PDCCH or PDSCH has been successfully received. 1-bit HARQ-ACK istransmitted in response to a single downlink codeword and 2-bit HARQ-ACKis transmitted in response to two downlink codewords. HARQ-ACK responsesinclude positive ACK (simply, ACK), negative ACK (NACK), DTX(Discontinuous Transmission) and NACK/DTX. Here, the term HARQ-ACK isused with HARQ ACK/NACK and ACK/NACK.

CSI (Channel State Information): This is feedback information about adownlink channel. MIMO-related feedback information includes an RI and aPMI.

The quantity of UCI that can be transmitted by a UE in a subframedepends on the number of SC-FDMA symbols available for controlinformation transmission. SC-FDMA symbols available for UCI correspondto SC-FDMA symbols other than SC-FDMA symbols used for reference signaltransmission in a subframe. In the case of a subframe including asounding reference signal (SRS), the SC-FDMA symbols available for UCIcorrespond to SC-FDMA symbols other than SC-FDMA symbols used forreference signal transmission and the last SC-FDMA symbol in thesubframe. A reference signal is used for PUCCH coherent detection. APUCCH supports various formats according to transmitted information.

PUCCH format 1 is used to transmit SR, PUCCH format 1a/1b is used totransmit ACK/NACK information, and PUCCH format 2 is used to carry CSIsuch as CQI/PMI/RI. PUCCH format 2a/2b is used to carry ACK/NACKinformation with CSI and PUCCH format 3 series is used to transmitACK/NACK information.

UCI Transmission

FIGS. 6 to 10 illustrate UCI transmission using PUCCH format 1 series,PUCCH format 2 series and PUCCH format 3 series.

In 3GPP LTE/LTE-A, a subframe having a normal CP is composed of twoslots each of which includes seven OFDM symbols (or SC-FDMA symbols). Asubframe having an extended CP is composed of two slots each of whichincludes six OFDM symbols (or SC-FDMA symbols). Since the number of OFDMsymbols (or SC-FDMA symbols) per subframe depends on a CP length, aPUCCH transmission structure in a UL subframe is varied according to CPlength. Accordingly, a method of transmitting UCI in a UL subframe by aUE is varied according to PUCCH format and CP length.

Referring to FIGS. 6 and 7, in case of transmission using PUCCH formats1a and 1b, the same control information is repeated on a slot basis in asubframe. UEs transmit ACK/NACK signals through different resourcescomposed of different cyclic shifts (CSs) of a CG-CAZAC(Computer-Generated Constant Amplitude Zero Auto Correlation) sequenceand orthogonal cover codes (OCC). A CS may correspond to a frequencydomain code and an OCC may correspond to a time domain spreading code.An OCC may also be called an orthogonal sequence. An OCC includes aWalsh/DFT (Discrete Fourier Transform) orthogonal code, for example.When the number of CSs is 6 and the number of OCCs is 3, a total of 18PUCCHs can be multiplexed in the same PRB (Physical Resource Block) onthe basis of a single antenna port. An orthogonal sequence w₀, w₁, w₂and w₃ may be applied in a time domain after FFT (Fast FourierTransform) or in a frequency domain before FFT. A PUCCH resource forACK/NACK transmission in 3GPP LTE/LTE-A is represented by a combinationof the position of a time-frequency resource (e.g. PRB), a cyclic shiftof a sequence for frequency spreading and an orthogonal code (orquasi-orthogonal code) for time spreading. Each PUCCH resource isindicated using a PUCCH resource index (PUCCH index). A slot levelstructure of PUCCH format 1 series for SR transmission is identical tothat of PUCCH formats 1a and 1b and a modulation method thereof isdifferent.

FIG. 8 illustrates transmission of CSI in a UL slot having a normal CPusing PUCCH format 2a/2b/2c and FIG. 9 illustrates transmission of CSIin a UL slot having an extended CP using PUCCH format 2a/2b/2c.

Referring to FIGS. 8 and 9, in case of the normal CP, a UL subframe iscomposed of 10 SC-FDMA symbols excepting symbols carrying UL referencesignals (RSs). CSI is coded into 10 transmission symbols (which may becalled complex-valued modulation symbols) through block coding. The 10transmission symbols are respectively mapped to 10 SC-FDMA symbols andtransmitted to an eNB.

PUCCH format 1/1a/1b and PUCCH format 2/2a/2b can carry only UCI havingup to a predetermined number of bits. However, as the quantity of UCIincreases due to introduction of carrier aggregation, a TDD system, arelay system and a multi-node system and an increase in the number ofantennas, a PUCCH format, which is called PUCCH format 3, capable ofcarrying a larger quantity of UCI than PUCCH formats 1/1a/1b/2/2a/2b, isintroduced. For example, PUCCH format 3 can be used for a UE for whichcarrier aggregation is set to transmit a plurality of ACK/NACK signalsfor a plurality of PDSCHs, received from an eNB through a plurality ofdownlink carriers, through a specific uplink carrier.

PUCCH format 3 may be configured on the basis of block spreading, forexample. Referring to FIG. 10, block spreading time-domain-spreads asymbol sequence using an OCC (or orthogonal sequence) and transmits thespread symbol sequence. According to block spreading, control signals ofa plurality of UEs can be multiplexed to the same RB and transmitted toan eNB. In the case of PUCCH format 2, one symbol sequence istransmitted over the time domain, and UCI of UEs is multiplexed using aCS of a CAZAC sequence and transmitted to an eNB. In the case of a newPUCCH format based on block spreading (e.g. PUCCH format 3), one symbolsequence is transmitted over the frequency domain, and UCI of UEs ismultiplexed using OCC based time-domain spreading and transmitted to theeNB. Referring to FIG. 8, one symbol sequence is spread using an OCChaving length-5 (that is, SF=5) and mapped to 5 SC-FDMA symbols. WhileFIG. 10 illustrates a case in which two RS symbols are used in one slot,3 RS symbols may be used and an OCC with SF=4 can be used for symbolsequence spreading and UE multiplexing. Here, the RS symbols can begenerated from a CAZAC sequence having a specific CS. A specific OCC canbe applied to/multiplied by the RS symbols and then the RS symbols canbe transmitted to the eNB. In FIG. 10, DFT may be applied prior to OCC,and FFT (Fast Fourier Transform) may replace DFT.

In FIGS. 6 to 10, a UL RS transmitted with UCI on a PUCCH can be usedfor the eNB to demodulate the UCI.

FIG. 11 illustrates multiplexing of UCI and uplink data in a PUSCHregion.

The uplink data can be transmitted in a data region of a UL subframethrough a PUSCH. A UL DMRS (Demodulation Reference Signal) correspondingto an RS for demodulation of the uplink data can be transmitted with theuplink data in the data region of the UL subframe. The control regionand the data region in the UL subframe are respectively called a PUCCHregion and a PUSCH region.

When UCI needs to be transmitted in a subframe to which PUSCHtransmission is assigned, a UE multiplexes the UCI and uplink data(referred to as PUSCH data hereinafter) prior to DFT-spreading andtransmits the multiplexed UL signal over a PUSCH if simultaneoustransmission of the PUSCH and a PUCCH is not allowed. The UCI includesat least one of CQI/PMI, HARQ ACK/NACK and RI. The number of REs used totransmit each of CQI/PMI, HARQ ACK/NACK and RI is based on a modulationand coding scheme (MCS) and an offset value (Δ_(offset) ^(CQI),Δ_(offset) ^(HARQ-ACk), Δ_(offset) ^(RI)) allocated for PUSCHtransmission. The offset value allows different coding rates accordingto UCI and is semi-statically set through higher layer (e.g. radioresource control (RRC)) signaling. The PUSCH data and UCI are not mappedto the same RE. The UCI is mapped such that it is present in both slotsof the subframe.

Referring to FIG. 11, CQI and/or PMI resource is located at the start ofthe PUSCH data, sequentially mapped to all SC-FDMA symbols in onesubcarrier and then mapped to the next subcarrier. The CQI/PMI is mappedto a subcarrier from the left to the right, that is, in a direction inwhich the SC-FDMA symbols index increases. The PUSCH data israte-matched in consideration of the quantity of a CQI/PMI resource(that is, the number of coded symbols). The same modulation order asthat of UL-SCH data is used for the CQI/PMI. ACK/NACK is inserted intopart of SC-FDMA resource to which the UL-SCH data is mapped throughpuncturing. The ACK/NACK is located beside a PUSCH RS for demodulationof the PUSCH data and sequentially occupies corresponding SC-FDMAsymbols from bottom to top, that is, in a direction in which thesubcarrier index increases. In a normal CP case, SC-FDMA symbols for theACK/NACK correspond to SC-FDMA symbols #2/#5 in each slot, as shown inFIG. 11. Coded RI is located beside a symbol for ACK/NACK irrespectiveof whether the ACK/NACK is actually transmitted in the subframe.

In 3GPP LTE, UCI may be scheduled such that it is transmitted over aPUSCH without PUSCH data. Multiplexing ACK/NACK, RI and CQI/PMI issimilar to that illustrated in FIG. 11. Channel coding and rate matchingfor control signaling without PUSCH data correspond to those for theabove-described control signaling having PUSCH data.

In FIG. 11, the PUSCH RS can be used to demodulate the UCI and/or thePUSCH data transmitted in the PUSCH region. In the present invention, aUL RS related to PUCCH transmission and a PUSCH RS related to PUSCHtransmission are commonly called a DMRS.

A sounding reference signal (SRS) (not shown) may be allocated to thePUSCH region. The SRS is a UL RS that is not related to transmission ofa PUSCH or PUCCH. The SRS is transmitted on the last SC-FDMA symbol of aUL subframe in the time domain and transmitted in a data transmissionband of the UL subframe, that is, a PUSCH region in the frequencydomain. An eNB can measure an uplink channel state between a UE and theeNB using the SRS. SRSs of a plurality of UEs, which aretransmitted/received on the last SC-FDMA symbol of the same subframe,can be discriminated according to frequency positions/sequences thereof.

Uplink Reference Signal

A DMRS transmitted in a PUCCH region and a DMRS and an SRS transmittedin a PUSCH region can be regarded as uplink UE-specific RSs because theyare UE-specifically generated by a specific UE and transmitted to aneNB.

A UL RS is defined by a cyclic shift of a base sequence according to apredetermined rule. For example, an RS sequence r_(u,v) ^((α))(n) isdefined by a cyclic shift α of a base sequence r_(u,v)(n) according tothe following equation.r _(u,v) ^((α))(n)=e ^(jαn) ·r _(u,v)(n), 0≦n<M _(sc) ^(RS)  [Equation1]

Here, M_(sc) ^(RS) is the length of the RS sequence, M_(sc)^(RS)=m·M_(sc) ^(RB) and 1≦m≦N_(RB) ^(max,UL). N_(RB) ^(max,UL)represented by a multiple of N_(sc) ^(RB) refers to a widest uplinkbandwidth configuration. N_(sc) ^(RB) denotes the size of an RB and isrepresented by the number of subcarriers. A plurality of RS sequencescan be defined from a base sequence through different cyclic shiftvalues α. A plurality of base sequences is defined for a DMRS and anSRS. For example, the base sequences are defined using a root Zadoff-Chusequence. Base sequences r_(u,v)(n) are divided into two groups each ofwhich includes one or more base sequences. For example, each basesequence group can include one base sequence having a length of M_(sc)^(RS)=m·N^(RB) (1≦m≦5) and two base sequences having a length of M_(sc)^(RS)m·N_(sc) ^(RB) (6≦m≦N_(sc) ^(RB)). As to r_(u,v)(n), uε{0, 1, . . ., 29} denotes a group number (that is, group index) and v denotes a basesequence number (that is, base sequence index) in the correspondinggroup. Each base sequence group number and a base sequence number in thecorresponding group may be varied with time.

The sequence group number u in a slot n_(s) is defined by a grouphopping pattern f_(gh)(n_(s)) and a sequence shift pattern f accordingto the following equation.u=(f _(gh)(n _(s))+f _(ss))mod 30  [Equation 2]

In Equation 2, mod refers to a modulo operation. A mod B means aremainder obtained by dividing A by B.

A plurality of different hopping patterns (e.g. 30 hopping patterns) anda plurality of different sequence shift patterns (e.g. 17 sequence shiftpatterns) are present. Sequence group hopping may be enabled or disabledaccording to a cell-specific parameter provided by a higher layer.

The group hopping pattern f_(gh)(n) can be provided by a PUSCH and aPUCCH according to the following equation.

$\begin{matrix}{{f_{gh}\left( n_{s} \right)} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu}{group}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}{{c\left( {{8\; n_{s}} + i} \right)} \cdot 2^{i}}} \right)\;{mod}\; 30} & {{if}\mspace{14mu}{group}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, a pseudo-random sequence c(i) can be defined by a length-31 Goldsequence. An output sequence c(n) (n=0, 1, . . . , M_(PN)−1) having alength of M_(PN) is defined according to the following equation.c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2x ₁(n−31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 4]

Here, N_(C)=1600 and the first m-sequence is initialized to x₁(0)=1,x₁(n)=0, n=1, 2, . . . , 30. Initialization of the second m-sequence isrepresented by the following equation having a value depending onapplication of the sequence.c _(init)=Σ_(i=0) ³⁰ x ₂(i)·2^(i)  [Equation 5]

In Equation 3, a pseudo-random sequence generator is initialized toc_(init) at the start of each radio frame according to the followingequation.

$\begin{matrix}{c_{init} = \left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In Equation 6, └ ┘ denotes floor operation and └A┘ is a maximum integerless than or equal to A.

According to 3GPP LTE, a PUCCH and a PUSCH have different sequence shiftpatterns although they have the same group hopping pattern according toEquation 3. A sequence shift pattern f_(ss) ^(PUCCH) for the PUCCH isprovided on the basis of cell identification information (cell ID)according to the following equation.f _(ss) ^(PUCCH) =N _(ID) ^(cell) mod 30  [Equation 7]

A sequence shift pattern f_(ss) ^(PUSCH) for the PUSCH is givenaccording to the following equation using the sequence shift patternf_(ss) ^(PUCCH) for the PUCCH and a value Δ_(ss) configured by a higherlayer.f _(ss) ^(PUSCH)=(f _(ss) ^(PUCCH)+Δ_(ss))mod 30  [Equation 8]

Here, Δ_(ss)ε{0, 1, . . . , 29}.

Base sequence hopping is applied only to RSs having a length of M_(sc)^(RS)≧6N_(sc) ^(RB). For RSs having a length of M_(sc) ^(RS)≧6N^(RB),the base sequence number v in a base sequence group is 0. For RSs havinga length of M_(sc) ^(RS)>6N^(RB), the base sequence number v in a basesequence group in the slot n_(s) is defined as v=c(n_(s)) when grouphopping is disabled and sequence hopping is enabled and defined as v=0in other cases. Here, the pseudo-random sequence c(i) is given byEquation 4. The pseudo-random sequence generator is initialized toc_(init) at the start of each radio frame according to the followingequation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

A sequence r_(PUCCH) ^((p))(·) of the UL RS (PUCCH DMRS) in FIGS. 6 to10 is given by the following equation.

$\begin{matrix}{{r_{PUCCH}^{(p)}\left( {{m^{\prime}N_{RS}^{PUCCH}M_{sc}^{RS}} + {mM}_{sc}^{RS} + n} \right)} = {\frac{1}{\sqrt{P}}{{\overset{\_}{w}}^{(p)}(m)}{z(m)}{r_{u,v}^{({\alpha{\_ p}})}(n)}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Here, m=0, . . . , N_(RS) ^(PUCCH)−1, n=0, . . . , M_(sc) ^(RS)−1, andm′=0, 1. N_(RS) ^(PUCCH) denotes the number of reference symbols perslot for the PUCCH and P denotes the number of antenna ports used forPUCCH transmission. A sequence r_(u,v) ^((α) ^(_) ^(p))(n) is given byEquation 1 having M_(sc) ^(RS)=12, and a cyclic shift α_p is determinedby a PUCCH format.

All PUCCH formats use a cell-specific CS, n_(cs) ^(cell)(n_(s),l) whichhas a value depending on a symbol number l and a slot number n_(s) andis determined as n_(cs) ^(cell)(n_(s), l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) isinitialized at the start of each radio frame according toc_(init)=N_(ID) ^(cell).

As to PUCCH formats 2a and 2B, z(m) corresponds to d(10) when m=1, andz(m)=1 in other cases. For PUCCH formats 2a and 2b supported for onlythe normal CP, UCI bits b(20), . . . , b(M_(bit)−1) from among b(0), . .. , b(M_(bit)−1) are modulated into a single modulation symbol d(10)used to generate a reference signal for PUCCH formats 2a and 2b, asshown in Table 1.

TABLE 1 PUCCH format b(20), . . . , b(M_(bit) − 1) d(10) 2a 0  1 1 −1 2b00  1 01 −j 10  j 11 −1

The PUSCH RS (referred to as PUSCH DMRS hereinafter) in FIG. 11 istransmitted on a layer basis. A PUSCH DMRS sequence r_(PUSCH) ^((p))(·)related to layer λε{0, 1, . . . , υ−1} is given by the followingequation.r _(PUSCH) ^((λ))(m·M _(sc) ^(RS) +n)=w ^((λ))(m)r _(u,v) ^((α) ^(_)^(λ))(n)  [Equation 11]

Here, m=0, 1, n=0, . . . , M_(sc) ^(RS)−1, and M_(sc) ^(RS)=M_(sc)^(PUSCH). M_(sc) ^(PUSCH) is a bandwidth scheduled for uplinktransmission and denotes the number of subcarriers. An orthogonalsequence w(λ)(m) can be given by Table 2 using a cyclic shift field inlatest uplink-related DCI for transport blocks related to thecorresponding PUSCH. Table 2 illustrates mapping of a cyclic shift fieldin an uplink-related DCI format to n_(DMRS,λ) ⁽²⁾ and [w^((λ))(0)w^((λ))(1)].

TABLE 2 Cyclic Shift Field in uplink-related n_(DMRS, λ) ⁽²⁾ [w^((λ))(0)w^((λ))(1)] DCI format λ = 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3000 0 6 3 9 [1 1] [1 1] [1 −1] [1 −1] 001 6 0 9 3 [1 −1] [1 −1] [1 1] [11] 010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] 011 4 10 7 1 [1 1] [1 1] [1 1][1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] 101 8 2 11 5 [1 −1] [1 −1] [1−1] [1 −1] 110 10 4 1 7 [1 −1] [1 −1] [1 −1] [1 −1] 111 9 3 0 6 [1 1] [11] [1 −1] [1 −1]

A cyclic shift α_λ in the slot n_(s) is given as 2πn_(cs,λ)/12. Here,n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS,λ) ⁽²⁾+n_(PN)(n_(s)))mod 12 wheren_(DMRS) ⁽¹⁾ is given by Table 3 according to a cyclic shift parameterprovided through higher layer signaling. Table 3 shows mapping of cyclicshifts to n_(DMRS) ⁽¹⁾ according to higher layer signaling.

TABLE 3 cyclicShift n_(DMRS) ⁽¹⁾ 0 0 1 2 2 3 3 4 4 6 5 8 6 9 7 10

Furthermore, n_(PN)(n_(s)) is given by the following equation using thecell-specific pseudo-random sequence c(i).n _(PN)(n _(s))=Σ_(i=0) ⁷ c(8N _(symb) ^(UL) ·n _(s)+i)·2^(i)  [Equation 12]

Here, the pseudo-random sequence c(i) is defined by Equation 4. Thepseudo-random sequence generator is initialized to c_(init) at the startof each radio frame according to the following equation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

An SRS sequence r_(SRS) ^((p))(n)=r_(u,v) ^((α) ^(_) ^(p))(n) is definedby Equation 1. Here, u denotes the PUCCH sequence group numberabove-described with respect to group hopping and v denotes the basesequence number above-described with respect to sequence hopping. Thecyclic shift α_p of the SRS is given as follows.

$\begin{matrix}{{\alpha_{p} = {2\;\pi\frac{n_{SRS}^{{cs},p}}{8}}}{n_{SRS}^{{cs},p} = {\left( {n_{SRS}^{cs} + \frac{8p}{N_{ap}}} \right)\;{mod}\; 8}}{p \in \left\{ {0,1,\ldots\mspace{14mu},{N_{ap} - 1}} \right\}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Here, n_(SRS) ^(cs)={0, 1, 2, 3, 4, 5, 6, 7} is a value configured foreach UE by higher layer parameters and separately generated by differenthigher layer parameters for configurations of periodic sounding andnon-periodic sounding. N_(ap) denotes the number of antenna ports usedfor SRS transmission.

Coordinated Multi-Point: CoMP

CoMP transmission/reception scheme (which is also referred to asco-MIMO, collaborative MIMO or network MIMO) is proposed to meetenhanced system performance requirements of 3GPP LTE-A. CoMP can improvethe performance of a UE located at a cell edge and increase averagesector throughput.

In a multi-cell environment having a frequency reuse factor of 1, theperformance of a UE located at a cell edge and average sector throughputmay decrease due to inter-cell interference (ICI). To reduce ICI, aconventional LTE system uses a method for allowing a UE located at acell edge in an interfered environment to have appropriate throughputusing a simple passive scheme such as fractional frequency reuse (FFR)through UE-specific power control. However, it may be more preferable toreduce ICI or reuse ICI as a signal that a UE desires rather thandecreasing frequency resource use per cell. To achieve this, CoMP can beapplied.

CoMP applicable to downlink can be classified into joint processing (JP)and coordinated scheduling/beamforming (CS/CB).

According to the JP, each point (eNB) of a CoMP coordination unit canuse data. The CoMP coordination unit refers to a set of eNBs used for acoordinated transmission scheme. The JP can be divided into jointtransmission and dynamic cell selection.

The joint transmission refers to a scheme through which PDSCHs aresimultaneously transmitted from a plurality of points (some or all CoMPcoordination units). That is, data can be transmitted to a single UEfrom a plurality of transmission points. According to jointtransmission, quality of a received signal can be improved coherently ornon-coherently and interference on other UEs can be actively erased.

Dynamic cell selection refers to a scheme by which a PDSCH istransmitted from one point (in a CoMP coordination unit). That is, datais transmitted to a single UE from a single point at a specific time,other points in the coordination unit do not transmit data to the UE atthe time, and the point that transmits the data to the UE can bedynamically selected.

According to the CS/CB scheme, CoMP coordination units cancollaboratively perform beamforming of data transmission to a single UE.Here, user scheduling/beaming can be determined according tocoordination of cells in a corresponding CoMP coordination unit althoughdata is transmitted only from a serving cell.

In case of uplink, coordinated multi-point reception refers to receptionof a signal transmitted according to coordination of a plurality ofpoints geographically spaced apart from one another. A CoMP receptionscheme applicable to uplink can be classified into joint reception (JR)and coordinated scheduling/beamforming (CS/CB).

JR is a scheme by which a plurality of reception points receives asignal transmitted over a PUSCH and CS/CB is a scheme by which userscheduling/beamforming is determined according to coordination of cellsin a corresponding CoMP coordination unit while one point receives aPUSCH.

A UE can receive data from multi-cell base stations collaborativelyusing the CoMP system. The base stations can simultaneously support oneor more UEs using the same radio frequency resource, improving systemperformance. Furthermore, a base station may perform space divisionmultiple access (SDMA) on the basis of CSI between the base station anda UE.

In the CoMP system, a serving eNB and one or more collaborative eNBs areconnected to a scheduler through a backbone network. The scheduler canoperate by receiving channel information about a channel state betweeneach UE and each collaborative eNB, measured by each eNB, through thebackbone network. For example, the scheduler can schedule informationfor collaborative MIMO operation for the serving eNB and one or morecollaborative eNBs. That is, the scheduler can directly directcollaborative MIMO operation to each eNB.

As described above, the CoMP system can be regarded as a virtual MIMOsystem using a group of a plurality of cells. Basically, a communicationscheme of MIMO using multiple antennas can be applied to CoMP.

Enhanced Uplink Signal Transmission Scheme

Referring to Equations 1 to 14, UEs located in a cell initialize thepseudo-random sequence generator that generates RS sequences using thesame N_(ID) ^(cell). Because a UE transmits an uplink signal only to onecell, the UE uses only one N_(ID) ^(cell) in order to generate a PUSCHDMRS, PUCCH DMRS and SRS. That is, in a conventional system in which aUE transmits an uplink signal only to one cell, a UE based DMRS sequenceis used. In other words, since the conventional communication systemperforms uplink transmission only for one cell, a UE can acquire N_(ID)^(cell) (i.e. physical layer cell ID) on the basis of a downlink PSS(Primary Synchronization Signal) received from the serving cell and usethe acquired N_(ID) ^(cell) to generate an uplink RS sequence.

However, in uplink CoMP, a UE can transmit an uplink signal to aplurality of cells or reception points (RPs) or to some of the cells orRPs. In this case, when an uplink transmitting side transmits an RSsequence generated according to a conventional method, a receiving sidemay not detect the RS.

Accordingly, for CoMP in which a plurality of cells or RPs participatesin communication with a UE, it is necessary to define DMRS generation,resource allocation and/or transmission schemes for data transmitted todifferent points even if the different points do not simultaneouslyreceive the data. While one RP can receive an uplink signal from a UEthrough one or more cells, a cell receiving an uplink signal is calledan RP in the following description for convenience.

The present invention proposes a method by which a CoMP UE generates aDMRS sequence used for PUSCH transmission and/or PUCCH transmission in amulti-cell (multi-RP) environment.

FIG. 12 is a diagram for explaining an exemplary UL CoMP operation.

In an uplink CoMP operation by which one UE (i.e. CoMP UE) transmits aPUSCH to a plurality of cells (or RPs), it is important to ensure mutualorthogonality between uplink DMRSs. If mutual orthogonality betweenuplink DMRSs is not ensured, each RP cannot correctly estimate an uplinkchannel, and thus PUSCH demodulation performance is considerablydeteriorated. The UE can generate a DMRS base sequence using the cell IDof a serving cell and apply an OCC for orthogonality with other DMRSs asnecessary. Specifically, the uplink DMRS base sequence is a function ofthe cell ID, and a PUSCH DMRS base sequence index having an offset ofΔ_(ss) from a PUCCH DMRS base sequence index is determined. Here, Δ_(ss)is given through higher layer signaling (e.g. RRC signaling). That is,the same cell ID is applied to generation of base sequences of PUCCHDMRS and PUSCH DMRS and a base sequence index offset of Δ_(ss) isprovided between the base sequences of PUCCH DMRS and PUSCH DMRS (referto Equation 8). For example, if Δ_(ss)=0 is signaled through RRCsignaling, the PUCCH DMRS and PUSCH DMRS may have the same basesequence.

In case of the CoMP UE, a DL serving cell and a UL serving cell may bedifferent from each other, and thus the cell ID of the DL serving cellcannot be used to generate a UL DMRS base sequence and the UL DMRS basesequence needs to be generated using the cell ID of an RP according todetermination by a scheduler. That is, the UL DMRS base sequence needsto be generated using the ID of a cell other than the serving cell. Toprovide scheduling flexibility in determination of UEs paired forMU-MIMO, it is desirable to dynamically indicate a cell ID used togenerate a UL DMRS. For example, a higher layer can signal setting of aplurality of DMRSs (including setting of a DMRS for cell A and settingof a DMRS for cell B) to a CoMP UE located at edges of a cell A and acell B shown in FIG. 12. The CoMP UE may be co-scheduled with another UE(UE-A) of the cell A or another UE (UE-B) of the cell B according tochannel condition and/or other network conditions. That is, a DMRS basesequence of the CoMP UE can be generated using the ID of a cell to whicha UE co-scheduled with the CoMP UE belongs. The cell ID used for DMRSbase sequence generation can be dynamically selected or indicated.

To support the above-described uplink CoMP operation, the presentinvention can provide a cell ID to be used to generate a PUSCH DMRSsequence to a UE through UE-specific higher layer signaling (e.g. RRCsignaling). The cell ID used to generate the PUSCH DMRS sequence can beindicated using a parameter such as N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) to be discriminated from a cell ID (that is, a parameterN_(ID) ^(cell) representing a physical layer cell ID (PCI)) used togenerate a conventional DMRS sequence. Here, N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be called a virtual cell ID (VCI) for PUSCH DMRS sequencegeneration. The virtual cell ID (referred to as “PUSCH DMRS VCI”) forPUSCH DMRS sequence generation may have a value identical to ordifferent from the PCI.

According to the conventional operation, a sequence shift pattern f_(ss)^(PUSCH) for the PUSCH DMRS is determined using a sequence shift patternf_(ss) ^(PUSCH) for the PUCCH and the sequence shift related offsetΔ_(ss) set by a higher layer (refer to Equations 7 and 8). When f_(ss)^(PUCCH) of Equation 7 is applied to Equation 8, the following equation15 is obtained.f _(ss) ^(PUSCH)=(N _(ID) ^(cell) mod 30)+Δ_(ss))mod 30=(N _(ID)^(cell)+Δ_(ss))mod 30  [Equation 15]

When use of the PUSCH DMRS VCI parameter (e.g. N_(ID) ^((PUSCH)) orn_(ID) ^((PUSCH))) is set by a higher layer, the offset Δ_(ss) set bythe higher layer may be used in the present invention. This may becalled a first scheme for setting Δ_(ss).

Furthermore, when use of the PUSCH DMRS VCI parameter (e.g. N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH))) is set by the higher layer, the presentinvention may generate a PUSCH DMRS sequence using a predetermined (orpre-appointed) specific offset value Δ_(ss) instead of the offset Δ_(ss)set by the higher layer. That is, when the higher layer signals thePUSCH DMRS VCI parameter (e.g. N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)))to a UE, the UE can be configured to use the predetermined offset Δ_(ss)instead of the offset Δ_(ss) previously used by the UE (or set by thehigher layer). This may be called a second scheme for setting Δ_(ss).

As an example of the second scheme for setting Δ_(ss), the presentinvention may previously determine a rule such that operation isperformed on the basis of Δ_(ss)=0 when the higher layer sets use of thePUSCH DMRS VCI parameter N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)). Thismay be called a third scheme for setting Δ_(ss).

For example, the PUSCH DMRS VCI parameter N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) can replace the physical cell ID parameter N_(ID) ^(cell) andΔ_(ss) can be set to 0 in Equation 15. This is arranged as follows.f _(ss) ^(PUSCH) =N _(ID) ^((PUSCH)) mod 30 orf _(ss) ^(PUSCH) =n _(ID) ^((PUSCH)) mod 30  [Equation 16]

A plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be set the higher layer and a value to be used from amongthe plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be dynamically indicated through uplink scheduling grantinformation (that is, uplink-related DCI). Here, when the PUSCH DMRS VCIvalues N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)) are set by the higherlayer, specific values respectively mapped to the PUSCH DMRS VCI valuesmay be used.

To dynamically indicate one of the PUSCH DMRS VCI values N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH)) through the uplink-related DCI, a bit(or bits) for indicating a virtual cell ID may be newly added to theuplink-related DCI format to explicitly indicate the corresponding VCIor an existing bit (or bits) may be reused. For example, a mappingrelationship can be established such that one of states of a 3-bit“Carrier Indicator” field or a 3-bit “Cyclic Shift for DMRS and OCCindex” field from among bit fields of the uplink-related DCI (e.g. DCIformat 0 or 4) implicitly indicates one of the PUSCH DMRS VCI valuesN_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)).

A case in which the PUSCH DMRS VCI N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) is set by the higher layer has been described in the aboveembodiment. The present invention proposes a scheme forsetting/providing a virtual cell ID (referred to as “PUCCH DMRS VCI”)used to generate a PUCCH DMRS sequence through UE-specific higher layersignaling (e.g. RRC signaling). A PUCCH DMRS VCI parameter may beindicated by N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)).

While the same cell ID (i.e. physical cell ID parameter N_(ID) ^(cell))is used to generate a PUSCH DMRS sequence and a PUCCH DMRS sequence inconventional operations, the present invention proposes a scheme ofseparately (independently) setting the PUSCH DMRS VCI (that is, N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH))) and the PUCCH DMRS VCI (that is, N_(ID)^((PUCCH)) or n_(ID) ^((PUCCH))).

For simplicity, the PUSCH DMRS VCI and the PUCCH DMRS VCI may berepresented as one parameter n_(ID) ^(RS). In this case, n_(ID) ^(RS)can be determined according to transmission type. That is, n_(ID) ^(RS)can be defined as n_(ID) ^((PUSCH)) in case of PUSCH relatedtransmission and n_(ID) ^(RS) can be defined as n_(ID) ^((PUCCH)) incase of PUCCH related transmission. Here, while one parameter n_(ID)^(RS) is used, n_(ID) ^((PUSCH)) (or N_(ID) ^((PUSCH))) and n_(ID)^((PUCCH)) (or n_(ID) ^((PUCCH))) are defined as separate parameters.That is, it should be understood that n_(ID) ^((PUSCH)) (or N_(ID)^((PUSCH)) and n_(ID) ^((PUCCH)) (or n_(ID) ^((PUCCH))) can be set by ahigher layer as separate parameters.

A case in which a PUCCH related VCI (that is, n_(ID) ^((PUCCH)) orN_(ID) ^((PUCCH))) and a PUSCH related VCI (that is, n_(ID) ^((PUCCH))or N_(ID) ^((PUCCH))) are different from each other may represent that aUE respectively transmits a PUCCH and a PUSCH to different RPs. That is,the PUCCH may be transmitted to an RP (or RPs) corresponding to, n_(ID)^((PUCCH)) or N_(ID) ^((PUCCH)) and the PUSCH may be transmitted to anRP (or RPs) corresponding to n_(ID) ^((PUCCH)) or N_(ID) ^((PUCCH)).

A plurality of PUCCH DMRS VCI values N_(ID) ^((PUCCH)) or n_(ID)^((PUCCH)) may be set by the higher layer and a value to be used fromamong the plurality of PUCCH DMRS VCI values N_(ID) ^((PUCCH)) or n_(ID)^((PUCCH)) may be dynamically indicated through uplink-related DCI. Todynamically indicate one of the PUCCH DMRS VCI values, a method ofimplicitly indicating a PUCCH DMRS VCI through a state of a specific bitfield of an uplink-related DCI format or a method of adding a new bitfield (or bit fields) to explicitly indicate a PUCCH DMRS DCI may beused. For example, a mapping relationship can be established such thatone of states of “HARQ process number” field (which is defined as 3 bitsin case of FDD and 4 bits in case of TDD) of an uplink-related DCIformat (e.g. DCI format 0 or 4) implicitly indicates one of the PUCCHDMRS VCI values. Otherwise, a mapping relationship can be establishedsuch that one of states of a bit field (e.g. downlink DMRS sequencegeneration can be performed using a scrambling ID value indicated by3-bit “Antenna port(s), scrambling identity and number of layers”field), which indicates a downlink DMRS (or UE-specific RS) parameter inDCI (e.g. DCI format 2C) for downlink allocation, implicitly indicatesone of the PUCCH DMRS VCI values.

The above-described embodiment of the present invention is representedby equations as follows.

When the pseudo-random sequence c(i) used to determine the group hoppingpattern f_(gh)(n_(s)) of an uplink DMRS is generated according toEquations 3 and 6, the present invention can initialize thepseudo-random sequence generator to c_(init) at the start of each radioframe according to the following equation. That is, Equation 6 can bereplaced by Equation 17.

$\begin{matrix}{c_{init} = \left\lfloor \frac{N_{ID}^{RS}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 17} \right\rbrack\end{matrix}$where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH, and n_(IS) ^(RS)=n_(ID) ^((PUCCH)) or n_(ID) ^(RS)=N_(ID)^((PUCCH)) for a PUCCH.

Equation 17 may be represented as Equation 18.

$\begin{matrix}{{{c_{init} = {{\left\lfloor \frac{N_{ID}^{({PUSCH})}}{30} \right\rfloor\mspace{14mu}{or}\mspace{14mu} c_{init}} = {\left\lfloor \frac{n_{ID}^{({PUSCH})}}{30} \right\rfloor\mspace{11mu}{for}\mspace{14mu}{PUSCH}}}},{and}}{c_{init} = {{\left\lfloor \frac{N_{ID}^{({PUCCH})}}{30} \right\rfloor\mspace{14mu}{or}\mspace{14mu} c_{init}} = {\left\lfloor \frac{n_{ID}^{({PUCCH})}}{30} \right\rfloor\mspace{14mu}{for}\mspace{14mu}{PUCCH}}}}} & \left\lbrack {{Equation}\mspace{14mu} 18} \right\rbrack\end{matrix}$

The sequence shift parameter f_(ss) ^(PUCCH) for PUCCH DMRS can berepresented by the following equation.f _(ss) ^(PUCCH) =n _(ID) ^(RS) mod 30  [Equation 19]where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUCCH.

Equation 19 may be represented as Equation 20.f _(SS) ^(PUCCH) =N _(ID) ^((PUCCH)) mod 30 or f _(SS) ^(PUCCH) =n _(ID)^((PUCCH)) mod 30

When the sequence shift parameter f_(ss) ^(PUSCH) for, PUSCH DMRS isdetermined, f_(ss) ^(PUSCH) can be represented by Equation 21 whenΔ_(ss) is predefined as 0 as represented by Equation 16.f _(SS) ^(PUSCH) =n _(ID) ^(RS) mod 30  [Equation 21]where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH.

Equation 21 may be represented as Equation 16 (that is, f_(ss)^(PUSCH)=N_(ID) ^((PUSCH)) mod 30 or f_(ss) ^(PUSCH)=n_(ID) ^((PUSCH))mod 30).

Here, it should be noted that n_(ID) ^((PUSCH)) (or N_(ID) ^((PUSCH)))and n_(ID) ^((PUCCH)) (or n_(ID) ^((PUCCH))), which are different fromeach other, are actually applied as VCI values (i.e. n_(ID) ^(RS))although f_(ss) ^(PUCCH) and f_(ss) ^(PUSCH) are defined in the sameequation form in Equations 19 and 21.

When the scheme (the third scheme for setting Δ_(ss)) represented byEquation 21 is applied, even if a value Δ_(ss) set through higher layersignaling has been provided to a corresponding UE, f_(ss) ^(PUSCH) iscalculated by setting Δ_(ss) to 0 when the PUSCH VCI (i.e. n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) is set by higher layer signaling.

Alternatively, in determination of the sequence shift parameter f_(ss)^(PUSCH) for PUSCH DMRS, f_(ss) ^(PUSCH) can be represented by Equation22 when the value Δ_(ss) set by the higher layer is used (that is, thefirst scheme for setting Δ_(ss)) or a predetermined specific valueΔ_(ss) is used (that is, the second scheme for setting Δ_(ss)).f _(SS) ^(PUSCH)={(n _(ID) ^(RS) mod 30)+Δ_(SS)} mod 30  [Equation 22]where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for PUSCH.

In Equation 22, Δ_(ss)ε{0, 1, . . . , 29}.

Equation 22 may be represented as the following equation.f _(SS) ^(PUSCH)={(N _(ID) ^((PUSCH)) mod 30)+Δ_(SS)} mod 30 orf _(SS) ^(PUSCH)={(n _(ID) ^((PUSCH)) mod 30)+Δ_(SS)} mod 30  [Equation23]

According to the first scheme for setting Δ_(ss), f_(ss) ^(PUSCH) can becalculated using the value Δ_(ss) set by higher layer signaling andpreviously provided to the corresponding UE and the PUSCH VCI (that is,n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) signaled by the higher layer.

According to the second scheme for setting Δ_(ss), even if the valueΔ_(ss) set by higher layer signaling has been provided to thecorresponding UE, f_(ss) ^(PUSCH) can be calculated by setting Δ_(ss) toa specific value s (sε{0, 1, . . . , 29}) when the PUSCH VCI (that is,n_(ID) ^(PUSCH)) or N_(ID) ^((PUSCH))) is set through higher layersignaling.

According to the above-described embodiments, a group hopping patternf_(gh)(n_(s)) of a UE for which a value A is set by a higher layer as aPUSCH DMRS VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH)))corresponds to group hopping patterns of other UEs (that is UEs forwhich a PCI is set to A and/or UEs for which a PUSCH VCI is set to A)using the value A as a cell ID. Furthermore, when the same Δ_(ss)(particularly, Δ_(ss)=0) is applied to determination of the sequenceshift pattern f_(ss) ^(PUSCH), the sequence shift pattern of the UE forwhich the PUSCH VCI is set corresponds to PUSCH DMRS sequence shiftpatterns of the other UEs. Accordingly, base sequence indexes u of UEswhich use the same group hopping pattern and the same sequence shiftpattern are identical (refer to Equation 2). This means thatorthogonality can be given between DMRSs of the UEs by respectivelyapplying different CSs to the UEs. That is, the present invention canprovide orthogonality between PUSCH DMRSs of UEs belonging to differentcells by setting a PUSCH DMRS VCI for a specific UE, distinguished froma conventional wireless communication system in which orthogonalitybetween PUSCH DMRSs is given using different CSs in the same cell.Accordingly, MU-MIMO pairing for UEs belonging to different cells can beachieved and enhanced UL CoMP operation can be supported.

Furthermore, even when different PUSCH DMRS VCI values are set for aplurality of UEs, orthogonality between PUSCH DMRSs can be provided bymaking the plurality or UEs use the same PUSCH DMRS base sequence.

Specifically, the first, second and third schemes for setting Δ_(ss)correspond to a rule of determining a value Δ_(ss) to be used when thePUSCH DMRS VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) issignaled by a higher layer. On the assumption that one of the schemes isapplied, an eNB can select an appropriate PUSCH DMRS VCI (that is,n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) in consideration of a valueΔ_(ss) to be used and signal the selected PUSCH DMRS VCI to a UE. Here,c_(init), which is a factor (or a seed value) for determining the grouphopping pattern f_(gh)(n), is determined as the same value for 30different VCI values (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))according to a floor operation as represented by Equations 17 and 18.Accordingly, it is possible to set f_(ss) ^(PUSCH) to a specific valueby selecting an appropriate one of the 30 different VCI valuesgenerating the same group hopping pattern f_(gh)(n_(s)). That is, grouphopping patterns f_(gh)(n_(s)) respectively calculated by two differentUEs can be identical to each other even though different VCIs are setfor the two UEs. Furthermore, sequence shift patterns f_(ss) ^(PUSCH)respectively calculated by the two UEs can be identical to each other.

An appropriate VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH)))that makes group hopping patterns f_(gh)(n_(s)) and sequence shiftpatterns f_(ss) ^(PUSCH) of MU-MIMO-paired UEs correspond to each othercan be set through a higher layer. Accordingly, PUSCH DMRS basesequences of the UEs become identical, and thus orthogonality betweenPUSCH DMRSs can be provided according to a method of applying differentCSs to the UEs.

In addition, a plurality of UEs can have the same group hopping patternf_(gh)(n_(s)) and/or the same sequence shift pattern f_(ss) ^(PUSCH)through a method of setting a UE-specific VCI (that is, n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) and/or a method of setting aUE-specific Δ_(ss). Here, since a method of additionallyhigher-layer-signaling a value Δ_(ss) to each UE may generateunnecessary overhead, it is possible to make the UEs have the same grouphopping pattern f_(gh)(n_(s)) and the same sequence shift pattern f_(ss)^(PUSCH) by signaling only the UE-specific VCI without separatelysignaling Δ_(ss).

Alternatively, the PUSCH transmission related VCI (that is, n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) may be used only when f_(ss) ^(PUSCH)is determined. That is, the PCI (that is, N_(ID) ^(cell)) of the currentserving cell is used for f_(ss) ^(PUCCH), as represented by Equation 7,and the VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) proposedby the present invention is used for f_(ss) ^(PUSCH) to separate a PUCCHsequence and a PUSCH sequence from each other.

Alternatively, N_(ID) ^((PUSCH)) may also be applied to f_(ss) ^(PUCCH).That is f_(ss) ^(PUCCH) can be defined by Equation 24.f _(SS) ^(PUCCH) =N _(ID) ^((PUSCH)) mod 30 or f _(SS) ^(PUCCH) =n _(ID)^((PUSCH)) mod 30  [Equation 24]

Equation 24 represents that a UE-specific VCI (N_(ID)) is set by higherlayer signaling and commonly used to determine f_(ss) ^(PUCCH) andf_(ss) ^(PUSCH). That is, a PUCCH and a PUSCH are transmitted from acorresponding UE to an RP (or RPs) using a UE-specific N_(ID) by settingthe UE-specific N_(ID).

The scope of the present invention is not limited to the above-describedembodiments and can include various methods for allowing UEs to have thesame PUSCH DMRS sequence group hopping pattern f_(gh)(n_(s)) and/or thesame shift pattern f_(ss) ^(PUSCH) by setting a UE-specific VCI.

When group hopping is disabled and sequence hopping is enabled, sequencehopping according to a conventional method can be defined as representedby Equation 9. As proposed by the present invention, when a UE-specificVCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) is set by a higherlayer and sequence hopping is enabled, the pseudo-random sequencegenerator can be initialized to c_(init) at the start of each radioframe according to the following equation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{n_{ID}^{RS}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 25} \right\rbrack\end{matrix}$where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH.

The VCI (that is, n_(ID) ^(RS) (n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID)^(RS)=N_(ID) ^((PUSCH)) for PUSCH transmission)) used in Equation 25 maycorrespond to the PUSCH DMRS VCI signaled to the UE through higher layersignaling, which is described in the other embodiments. In addition,f_(ss) ^(PUSCH) in Equation 25 may correspond to the value determinedaccording to Equation 16, 21, 22 or 23 (that is, a value determinedaccording to the first, second or third scheme for setting Δ_(ss)).

Specifically, n_(ID) ^(RS) and f_(ss) ^(PUSCH) in Equation 25 can usethe same values as n_(ID) ^(RS) and f_(ss) ^(PUSCH) determined to makegroup hopping patterns f_(gh)(n) and sequence hopping patterns f_(ss)^(PUSCH) set for MU-MIMO-paired UE equal to each other when the thirdscheme (that is, a scheme of determining Δ_(ss) as 0 without additionalhigher layer signaling for setting Δ_(ss)) for setting Δ_(ss) isapplied.

Scheme of Setting Range of Virtual Cell ID Value

As described above, the first VCI (e.g., n_(ID) ^((PUSCH)) or N_(ID)^((PUSCH))) for the PUCCH DMRS and the second VCI (e.g., n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) for the PUSCH DMRS can be provided asseparate parameters.

Here, the first VCI (e.g., n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) forthe PUCCH DMRS can be set to one of 504 values (i.e. 0 to 503) like thePCI. In the conventional wireless communication system, the sequenceshift pattern f_(ss) ^(PUCCH) for a PUCCH is calculated without usingΔ_(ss) according to Equation 7, f_(ss) ^(PUCCH)=N_(ID) ^(cell) mod 30.When the first VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) for aPUCCH is set through higher layer signaling according to the presentinvention, f_(ss) ^(PUCCH) is calculated without using Δ_(ss) accordingto Equation 20, f_(SS) ^(PUCCH)=N_(ID) ^((PUCCH)) mod 30 or f_(SS)^(PUCCH)=n_(ID) ^((PUCCH)) mod 30. Accordingly, sequence shift operationcan be successfully supported even when the range of the first VCI for aPUCCH is limited to 0 to 503 as the PCI.

When the second VCI (e.g., n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) for aPUSCH has the same range as that of the PCI, sequence shift for thePUSCH DMRS cannot be successfully supported. In the conventionalwireless communication system, the sequence shift pattern f_(ss)^(PUSCH) for a PUSCH is calculated with using Δ_(ss) according toEquation 8, f_(ss) ^(PUCCH)=(f_(ss) ^(PUCCH)+Δ_(ss))mod 30. According tothe scheme (particularly, the third scheme for setting Δ_(ss)) proposedby the present invention, however, when the second VCI (e.g. n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) for a PUSCH is set, f_(ss) ^(PUSCH) iscalculated without using Δ_(ss) according to Equation 16, f_(ss)^(PUSCH)=N_(ID) ^((PUSCH)) mod 30 or f_(ss) ^(PUSCH)=n_(ID) ^((PUSCH))mod 30. The scheme of using the PCI and Δ_(ss) in the conventionalwireless communication system was employed in order to cover 30 basesequence groups and 17 sequence group hopping patterns. That is, theoffset value Δ_(ss) was additionally used because all 510 (that is, 30base sequence groups×17 sequence group hopping patterns) cases cannot becovered when based on only the PCI since the range of the PCI is limitedto 0 to 503. Accordingly, to determine f_(ss) ^(PUSCH) using only thesecond VCI for a PUSCH without using Δ_(ss), it is necessary to correctthe range of the second VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID)^((PUSCH))).

Therefore, the present invention defines the range of the value of thesecond VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) as 0 to 509. Inthis case, it is possible to cover all the 510 (30×17) cases accordingto different base sequence groups and different sequence group hoppingpatterns.

Definition/setting/provision of the first VCI (e.g. n_(ID) ^((PUSCH)) orN_(ID) ^((PUSCH))) for the PUCCH DMRS and the second VCI (e.g., n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) for the PUSCH DMRS as separateparameters may mean that the available range (i.e. 0 to 503) of thefirst VCI and the available range (i.e. 0 to 509) of the second VCI aredifferent from each other.

UE Operation Relating to Uplink Reference Signal Generation

A scheme (referred to as a scheme A hereinafter) for supporting backwardcompatibility) in consideration of operation of a UE (referred to aslegacy-UE hereinafter) according to the legacy wireless communicationsystem and a scheme (referred to as a scheme B hereinafter) optimizedfor operation of a UE (advanced-UE (A-UE)) according to an advancedwireless communication system will be described in detail on the basisof the above-described uplink reference signal generation schemeaccording to the present invention.

The scheme A can be considered to be related to the first scheme (i.e.scheme of using Δ_(ss) set by a higher layer without change) for settingΔ_(ss) and the scheme B can be considered to be related to the second orthird scheme (i.e. scheme of ignoring Δ_(ss) set by a higher layer andusing a specific value of Δ_(ss) (particularly, Δ_(ss)=0) for settingΔ_(ss). However, the schemes A and B are not limited to the first,second and third schemes for setting Δ_(ss).

Scheme A

An uplink reference signal generation operation capable of supportingbackward compatibility with the legacy wireless communication system andUE operation will now be described. A UE can acquire the cell-specificparameter Δ_(ss) for UL RS sequence generation during initial cellaccess such as a random access procedure through higher layer signaling.In addition, the UE can acquire the PCI (that is, N_(ID) ^(cell)) of thecorresponding cell on the basis of PSS and SSS.

The UE can calculate f_(ss) ^(PUSCH) for PUSCH transmission using theacquired PCI and Δ_(ss) (refer to Equation 8), and thus the UE cancalculate a cyclic shift hopping (CSH) pattern of a PUSCH DMRS (refer toEquations 12 and 13). Here, an initial value c_(init) ^(CSH) of apseudo-random sequence c(i) that determines the CSH pattern can berepresented by equation 26 when f_(ss) ^(PUSCH) in Equation 13 isreplaced by f_(ss) ^(PUSCH) in equation 8 and f_(ss) ^(PUSCH) inEquation 6 is replaced by f_(SS) ^(PUCCH) in equation 7.

$\begin{matrix}{\left. {c_{init}^{CSH} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + {\left( {\left( {N_{ID}^{cell}\;{mod}\; 30} \right) + \Delta_{ss}} \right)\;{mod}\; 30}}} \right) = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + \left( {\left( {N_{ID}^{cell} + \Delta_{ss}} \right)\;{mod}\; 30} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 26} \right\rbrack\end{matrix}$

That is, the UE can acquire a parameter set {PCI, Δ_(ss), c_(init)^(CSH)} in the initial access procedure and thus can generate a UL RSsequence.

Scheme A-1

PUCCH DMRS, PUSCH DMRS and SRS sequences can be generated by applyingthe parameter set {PCI, Δ_(ss), c_(init) ^(CSH)} to Equations 1 to 14.Here, since the PCI corresponds to n_(ID) ^(cell), the above descriptionof Equations 1 to 14 can be equally applied and thus redundantdescription is omitted for clarity.

Scheme A-2

In addition, a UL RS generation operation of the UE, proposed by thepresent invention, when VCI and CSH pattern seed values are provided tothe UE will now be described.

For example, {VCI(m), c_(init) ^(CSH)(m)} (m=0, 1, 2, . . . ) may beprovided to the UE at a specific time through UE-specific higher layersignaling (e.g. RRC signaling). Here, m is a parameter set index. Forexample, when M PUCCH DMRS setting sets are present and m indicates oneof the M sets, m can have one of values of 0 to M−1. If L PUSCH DMRSsetting sets are present and m indicates one of the L sets, m can haveone of values of M, M+1, . . . , M+L−1. When N SRS setting sets arepresent and m indicates one of the N sets, m can have one of values ofM+L, M+L+1, . . . , M+L+N−1.

Here, a plurality of sets of {VCI(m), c_(init) ^(CHS)(m)} can besemi-statically provided through higher layer signaling, and the valueof the specific index m indicating one of the sets, which will be usedby the UE, can be dynamically signaled (e.g. L1/L2 signaled).

It is assumed that the number of PUCCH DMRS setting sets is M=1 in thefollowing description. That is, while a plurality of PUCCH DMRS settingsets can be given and one of the sets can be dynamically switched andapplied, it is assumed that a VCI for PUCCH DMRS generation isdetermined as VCI^(PUCCH)=VCI(0) and a seed value for a CSH pattern ofthe PUCCH DMRS is determined as c_(init) ^(CSH) ^(_) ^(PUCCH)=c_(init)^(CSH)(0) using a set {VCI(0), c_(init) ^(CSH)(0)} corresponding to asemi-statically set index m=0 for the PUCCH DMRS in the followingdescription. Here, semi-static setting of {VCI(0), c_(init) ^(CSH)(0)}corresponding to m=0 means that {VCI(0), c_(init) ^(CSH)(0)} can bechanged at a relatively long interval. Since a PUCCH is a controlchannel for stably carrying UCI, semi-static DMRS sequence change can bepreferable. However, the present invention does not exclude provision ofUE-specific higher layer signaling to set a PUCCH DMRS according to ascheme using M of larger than 2.

According to a conventional scheme, c_(init) ^(CSH) for a PUCCH DMRS wasdefined as c_(init) ^(CSH) ^(_) ^(PUCCH)=PCI. When VCI^(PUCCH) isprovided to the UE, the present invention provides c_(init) ^(CSH) ^(_)^(PUCCH) defined separately (or independently) of VCI^(PUCCH) throughUE-specific higher layer signaling, instead of determining c_(init)^(CSH) ^(_) ^(PUCCH) as c_(init) ^(CSH) ^(_) ^(PUCCH)=VCI^(PUCCH)according to the conventional scheme. Accordingly, even when differentvalues of VCI^(PUCCH) are set for MU-MIMO-paired UEs (the same basesequence can be determined even if different values of VCI^(PUCCH) areset), an OCC can be applied to DMRSs of the paired UEs to provideorthogonality by setting the same c_(init) ^(CSH) ^(_) ^(PUCCH). Thatis, according to the present invention, VCI^(PUCCH) and c_(init) ^(CSH)^(_) ^(PUCCH), which are independent parameters, can be set throughUE-specific higher layer signaling, and thus MU-MIMO pairing(particularly, inter-cell UE pairing) using an OCC can be supported.

An operation of the UE to generate a UL RS when M=1 (i.e. the number ofPUCCH DMRS setting sets is 1) and L=1 (i.e. the number of PUSCH DMRSsetting sets is 1) will now be described. The following description isfor clarity and the present invention can be equally applied to cases inwhich one or more of M, L and N have a value larger than 1.

Scheme A-2-i

When M=1 and L=1, {VCI(0), c_(init) ^(CSH)(0)} is defined as a PUCCHparameter set, as described above. Provision of c_(init) ^(CSH)(0)through higher layer signaling may mean that a PUCCH CSH pattern needsto be determined using c_(init) ^(CSH)(0) explicitly providedindependently of VCI(0). In this case, dynamic indication (or dynamicswitching) between the PCI basically provided to the UE and the VCI(0)may be signaled through a specific DCI format.

When c_(init) ^(CSH)(0) is not provided through higher layer signalingand only VCI(0) is provided, c_(init) ^(CSH) ^(_) ^(PUCCH) can bedetermined as c_(init) ^(CSH) ^(_) ^(PUCCH)=VCI(0). In this case,dynamic indication between the PCI and VCI(0) may be signaled through aspecific DCI format.

Here, {VCI(1), c_(init) ^(CSH)(1)} is defined as a PUSCH DMRS parameterset because L=1. Provision of c_(init) ^(CSH)(1) through higher layersignaling may mean that a PUSCH CSH pattern needs to be determined usingc_(init) ^(CSH)(1) explicitly given independently of VCI(1) instead ofbeing based on VCI(1) as in the conventional method. In this case,dynamic indication between PUSCH parameter set {VCI(1), c_(init)^(CSH)(1)} proposed by the present invention and the legacy parameterset {PCI, Δ_(ss), c_(init) ^(CSH)} may be signaled throughuplink-related DCI.

Scheme A-2-ii

This scheme represents application of the scheme A-2-i as a mathematicalexpression when M=1 and L=1. That is, the following embodiments of thepresent invention can be regarded as schemes for supporting generationof a UL RS having backward compatibility with the legacy system in termsof UE operation. That is, in a system defining 3GPP LTE release-10,forms or calculation processes of equations (refer to descriptionrelated to Equations 1 to 14) used for the UE to generate a UL RS aremaintained without change and parameters applied to the equations arereplaced by VCI(m), f_(ss) ^(PUCCH)(m), c_(init) ^(CSH)(m), etc.proposed by the present invention.

Specifically, the group hopping pattern f_(gh)(n_(s)) for a PUSCH and aPUCCH is defined as in Equation 3. However, the pseudo-random sequencec(i) can be defined such that it is initialized to

$c_{init} = \left\lfloor \frac{{VCI}(m)}{30} \right\rfloor$at the start of each radio frame by modifying Equation 6. Here, VCI(0)may correspond to the first VCI for the PUCCH and VCI(1) may correspondto the second VCI for the PUSCH.

The sequence shift pattern f_(ss) may be defined separately for thePUCCH and PUSCH. f_(ss) ^(PUCCH) for the PUCCH (i.e. m=0) can bedetermined as f_(ss) ^(PUCCH)(m)=VCI(m)mod 30 by modifying Equation 7and f_(ss) ^(PUSCH) for the PUSCH (i.e. m=1) can be determined as f_(ss)^(PUSCH)(m)=(f_(ss) ^(PUCCH)(m)+Δ_(ss))mod 30 by modifying Equation 8.Here, Δ_(ss)ε{0, 1, . . . , 29}, which can be set by a higher layer.

While sequence hopping is applied only to RSs corresponding to MR_(sc)^(RS)≧6N_(sc) ^(RB) as in the conventional scheme, the pseudo-randomsequence generator with respect to sequence hopping can be defined suchthat it is initialized to

$c_{init} = {{\left\lfloor \frac{{VCI}(m)}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$at the start of each radio frame by modifying Equation 9.

A cyclic shift value α₂ for the PUSCH (that is, m=1) in slot n_(s) isgiven as α_(λ)=2πn_(cs,λ)/12 where n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS)⁽²⁾+n_(PN)(n_(s)))mod 12, as described with reference to Table 3. Here,a pseudo-random sequence generator for n_(PN)(n_(s)) may be defined suchthat it is initialized at the start of each radio frame according to

$c_{init}^{{CSH}\;\_\;{PUSCH}} = {{\left\lfloor \frac{{VCI}(m)}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$or initialized according to c_(init) ^(CSH) ^(_) ^(PUSCH)=c_(init)^(CSH)(m) by modifying Equation 13.

In addition, all PUCCH (i.e. m=0) formats use the cell-specific CS,n_(cs) ^(cell)(n_(s),l). n_(cs) ^(cell)(n_(s),l) has different valuesaccording to a symbol number l and slot number n_(s) and is determinedaccording to n_(cs) ^(cell)(n_(s),l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) can bedefined such that it is initialized at the start of each radio frameaccording to c_(init) ^(CSH) ^(_) ^(PUCCH)=VCI or c_(init) ^(CSH) ^(_)^(PUCCH)=c_(init) ^(CSH)(m).

Scheme A-2-iii

It is assumed that M=1 and L=1 as described in the A-2-i and A-2-iischemes. According to the present scheme, a base sequence generated bythe UE is identical to a base sequence generated by a UE′ of a targetcell. Particularly, the present scheme relates to a method ofdetermining a VCI such that the base sequence generated by the UE isidentical to the base sequence generated by the UE′ of the target cellwhile a network signals only the VCI to the UE through higher layersignaling. For example, when a specific cell signals the PUSCH VCI(1) tothe UE through higher layer signaling, if the UE′ of the target celluses PCI′ and Δ_(ss)′ provided by the target cell and a base sequence ofthe UE′, which is generated according to f_(ss) ^(PUCCH)′=PCI′ mod 30and f_(ss) ^(PUSCH)′=(f_(ss) ^(PUCCH)′+Δ_(ss)′)mod 30 is present, VCI(1)can be determined as follows.

$\begin{matrix}{{{VCI}(1)} = {\left( {30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor} \right) + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 27} \right\rbrack\end{matrix}$

In addition, f_(ss) ^(PUSCH) can be arranged as Equation 28.

$\begin{matrix}\begin{matrix}{f_{ss}^{PUSCH} = {\left( {f_{ss}^{{PUSCH}^{\prime}} + 30 - \Delta_{ss}} \right){mod}\; 30}} \\{= {\left( {{f_{ss}^{{PUCCH}^{\prime}}\Delta_{ss}^{\prime}} + 30 - \Delta_{ss}} \right){mod}\; 30}} \\{= {\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime} - \Delta_{ss}} \right){mod}\; 30}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 28} \right\rbrack\end{matrix}$

When Equation 28 is applied to Equation 27, the following equation isobtained.

$\begin{matrix}{{{VCI}(1)} = {\left( {30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor} \right) + {\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime} - \Delta_{ss}} \right){mod}\; 30}}} & \left\lbrack {{Equation}\mspace{14mu} 29} \right\rbrack\end{matrix}$

When the eNB provides the value of VCI(1), determined according toEquation 29, to the UE, the UE can generate the same base sequence asthat of the UE′ of the specific target cell.

The meaning of the above equation is as follows. f_(ss) ^(PUSCH)′ of thecell to which the UE′ belongs equals

${\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime}} \right){mod}\; 30\mspace{14mu}{and}\mspace{14mu} f_{ss}^{{PUCCH}^{\prime}}} = {{PCI}^{\prime}{mod}\; 30.\mspace{14mu} 30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor}$can be determined such that it has the same value as the integer part(or quotient) of PCT/30 of the target cell to which the UE′ belongs. Inaddition, (f_(ss) ^(PUCCH)′+Δ_(ss)′−Δ_(ss))mod 30 can be determined suchthat it has the same value as the modulo part (or remainder) of

$\frac{{PCI}^{\prime}}{30}$of the target cell to which the UE′ belongs in order to consider Δ_(ss)′used by the target cell and to previously eliminate Δ_(ss) used as acell-specific value in the cell to which the UE belongs. When VCI(1)determined according to Equation 29 is signaled to the UE, the UEcalculates f_(ss) ^(PUSCH) according to f_(ss) ^(PUSCH)=({VCI(1)mod30}+Δ_(ss))mod 30 only by replacing n_(ID) ^(cell) by VCI(1) while usingEquations 7 and 8. Here, when the UE calculates f_(ss) ^(PUSCH), Δ_(ss)is eliminated and Δ_(ss)′ is left and thus the UE can generate the samebase sequence as that of the UE′.

The above description of the scheme of setting a VCI for the UE of thespecific cell such that the UE generates the same base sequence as thatof the UE′ of the target cell is exemplary. That is, variousmodifications or modified equations for determining a modulo part of aVCI according to the scheme of previously eliminating Δ_(ss) of a cellto which a CoMP UE belongs and the scheme of reflecting Δ_(ss)′ of thetarget cell are within the scope of the present invention.

Scheme B

Scheme B is applicable to the A-UE which is not limited to theconventional calculation method, according to the conventional scheme(e.g. scheme described with reference to Equations 1 to 14) or a schemeof newly defining only parameters of the conventional scheme.

Scheme B-1

The UE can acquire a parameter set {PCI, Δ_(ss), c_(init) ^(CSH)} in aninitial access procedure and thus generate a UL RS sequence. Here, PUCCHDMRS, PUSCH DMRS and SRS sequences can be generated by applying theparameter set {PCI, Δ_(ss), c_(init) ^(CSH)} to Equations 1 to 14, asdescribed in scheme A-1.

Scheme B-2

In addition, a UL RS generation operation of the UE when the UE receives{VCI(m), c_(init) ^(CSH)(m)} (m=0, 1, 2, . . . ) at a specific timethrough UE-specific higher layer signaling (e.g. RRC signaling) isdescribed below.

Scheme B-2-i

A UL RS generation operation of the UE on the assumption that M=1 (i.e.the number of PUCCH DMRS setting sets is 1) and L=1 (i.e. the number ofPUSCH DMRS setting sets is 1) may be identical to that described in thescheme A-2-i. However, the principle of the present invention can beequally applied to cases in which one of M, L and N has a value oflarger than 1.

Scheme B-2-ii

This scheme represents application of the scheme B-2-i as a mathematicalexpression when M=1 and L=1. That is, the following embodiments of thepresent invention relate to schemes defined differently from UEoperation according to the legacy system. That is, the followingembodiments relate to a method of calculating base sequence generationin a manner different from the conventional method rather than a methodof using the conventional scheme (scheme described with reference toEquations 1 to 14) or newly defining (or replacing) only a parameter inthe conventional scheme.

Specifically, the group hopping pattern f_(gh)(n_(s)) for a PUSCH and aPUCCH is defined as in Equation 3. However, the pseudo-random sequencec(i) can be defined such that it is initialized to

$c_{init} = \left\lfloor \frac{{VCI}(m)}{30} \right\rfloor$at the start of each radio frame by modifying Equation 6. Here, VCI(0)may correspond to the first VCI for the PUCCH and VCI(1) may correspondto the second VCI for the PUSCH.

The sequence shift pattern f_(ss) may be defined separately for thePUCCH and PUSCH. f_(ss) ^(PUCCH) for the PUCCH (i.e. m=0) can bedetermined as f_(ss) ^(PUCCH)(m)=VCI(m)mod 30 by modifying Equation 7.f_(ss) ^(PUCCH) for the PUSCH (i.e. m=1) can be determined as f_(ss)^(PUCCH)(m)=VCI(m)mod 30, different from Equation 8. That is, even ifVCI(0) for the PUCCH and VCI(1) for the PUSCH are different from eachother, f_(ss)(m) for the PUCCH and PUSCH can be commonly defined asf_(ss)(m)=VCI(m) mod 30.

While sequence hopping is applied only to RSs corresponding to M_(sc)^(RS)≧6N_(sc) ^(RB) as in the conventional scheme, the pseudo-randomsequence generator with respect to sequence hopping can be defined suchthat it is initialized to

$c_{init} = {{\left\lfloor \frac{{VCI}(m)}{30} \right\rfloor \cdot 2^{5}} + {f_{ss}(m)}}$at the start of each radio frame by modifying Equation 9.

A cyclic shift value α₂ for the PUSCH (that is, m=1) in slot n_(s) isgiven as α₂=2πn_(cs,λ)/12 where n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS,λ)⁽²⁾+n_(PN)(n_(s)))mod 12, as described with reference to Table 3. Here,a pseudo-random sequence generator for n_(PN)(n_(s)) may be defined suchthat it is initialized at the start of each radio frame according to

$c_{init}^{{CSH}\;\_\;{PUSCH}} = {{\left\lfloor \frac{{VCI}(m)}{30} \right\rfloor \cdot 2^{5}} + {f_{ss}(m)}}$or initialized according to c_(init) ^(CSH) ^(_) ^(PUSCH)=c_(init)^(CSH)(m) by modifying Equation 13.

In addition, all PUCCH (i.e. m=0) formats use the cell-specific CS,n_(cs) ^(cell)(n_(s),l). n_(cs) ^(cell)(n_(s),l) has different valuesaccording to a symbol number l and slot number n_(s) and is determinedaccording to n_(cs) ^(cell)(n_(s),l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) can bedefined such that it is initialized at the start of each radio frameaccording to c_(init) ^(CSH) ^(_) ^(PUSCH)=VCI(m) or c_(init) ^(CSH)^(_) ^(PUCCH)C_(init) ^(CSH)(m).

According to the scheme B-2-ii, the UL RS sequence generation operationof the UE can be simplified and optimized. For example, a newcalculation method for determining the sequence shift pattern accordingto f_(ss)(m)=VCI(m)mod 30 is provided. That is, if VCI(m) is providedthrough RRC signaling, the operation may be represented on theassumption that Δ_(ss)=0 all the time. In other words, the cell-specificvalue Δ_(ss) previously provided to the UE (i.e. previously set by ahigher layer) is not used any more after the UE receives VCI(m).

Scheme B-2-iii

It is assumed that M=1 and L=1 as described in the B-2-i and B-2-iischemes. According to the present scheme, a base sequence generated bythe UE is identical to a base sequence generated by a UE′ of a targetcell. Particularly, the present scheme relates to a method ofdetermining a VCI such that the base sequence generated by the UE isidentical to the base sequence generated by the UE′ of the target cellwhile a network signals only the VCI to the UE through higher layersignaling. For example, when a specific cell signals the PUSCH VCI(1) tothe UE through higher layer signaling, if the UE′ of the target celluses PCI′ and Δ_(ss)′ provided by the target cell and a base sequence ofthe UE′, which is generated according to f_(ss) ^(PUCCH)′=PCI′ mod 30and f_(ss) ^(PUSCH)′=(f_(ss) ^(PUCCH)′+Δ_(ss)′)mod 30 is A present,VCI(1) can be determined as follows.

$\begin{matrix}\begin{matrix}{{{VCI}(1)} = {\left( {30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor} \right) + f_{ss}^{PUSCH}}} \\{= {\left( {30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor} \right) + {f_{ss}(m)}}} \\{= {\left( {30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor} \right) + {{{VCI}(1)}{mod30}}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 30} \right\rbrack\end{matrix}$

When the eNB provides the value of VCI(1), determined according toEquation 30, to the UE, the UE can generate the same base sequence asthat of the UE′ of the specific target cell.

The meaning of the above equation is described. f_(ss) ^(PUCCH)′ of thecell to which the UE′ belongs equals

${\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime}} \right){mod}\; 30\mspace{14mu}{and}\mspace{14mu} f_{ss}^{{PUCCH}^{\prime}}} = {{PCI}^{\prime}{mod}\; 30.\mspace{14mu} 30 \times \left\lfloor \frac{{PCI}^{\prime}}{30} \right\rfloor}$can be determined such that it has the same value as the integer part(or quotient) of

$\frac{{PCI}^{\prime}}{30}$of the target cell to which the UE′ belongs. In addition, f_(ss)^(PUCCH)′ is determined in consideration of only Δ_(ss)′ (that is, UEassumes Δ_(ss)=0 all the time) used in the target cell such that f_(ss)^(PUCCH)′ has the same value as the modulo part (or remainder) of

$\frac{{PCI}^{\prime}}{30}$of the target cell to which the UE′ belongs. When VCI(1) determinedaccording to Equation 30 is signaled to the UE, the UE can simplycalculate f_(ss) according to f_(ss)(m)=VCI(1)mod 30 and can generatethe same base sequence as that of the UE′ because Δ_(ss)′ has beenreflected in f_(ss).

The above description of the scheme of setting a VCI for the UE of thespecific cell such that the UE generates the same base sequence as thatof the UE′ of the target cell is exemplary. That is, variousmodifications or modified equations for determining a modulo part of aVCI according to the scheme of reflecting only Δ_(ss)′ of the targetcell.

In the embodiments for describing the schemes A and B, M, L and N may bearbitrary values and, when each of M, L and N is larger than 1, aspecific one of a plurality of RS setting parameter sets correspondingthereto can be dynamically indicated (dynamically switched) through aDCI format.

When N for SRS sequence generation is larger than 1, the CoMP UE cangenerate a plurality of SRS sequences. Furthermore, even if M, L and Nare larger than 1, the cell-specific parameter set (i.e. {PCI, Δ_(ss),c_(init) ^(CSH)}) of the corresponding cell, which is initially acquiredby the UE, can be included in the dynamically indicated RS settingparameter sets such that the cell-specific parameter set is applied as adefault set (i.e. applied in the form of a fall-back mode).

While operations capable of efficiently supporting CoMP operation usingan uplink DMRS have been described above, the scope of the presentinvention is not limited thereto and the principle of the presentinvention can be equally applied to other uplink RStransmission/reception schemes.

FIG. 13 is a flowchart illustrating a method for transmitting an uplinkDMRS according to an embodiment of the present invention.

A UE may receive a VCI (e.g. n_(ID) ^(RS)) from an eNB through higherlayer signaling (e.g. RRC signaling) in step S1310. Here, a first VCI(e.g. n_(ID) ^(PUCCH)) for a PUCCH DMRS and a second VCI (e.g. n_(ID)^(PUSCH)) for a PUSCH DMRS may be signaled/set as separate parameters(that is, independent parameters).

The UE may generate an RS sequence (e.g. a PUCCH DMRS sequence and/or aPUSCH DMRS sequence) in step S1320. The embodiments of the presentinvention may be applied to DMRS sequence generation. For example, whenthe VCI is set by a higher layer, a group hopping pattern, a sequenceshift pattern, sequence hopping and/or CS hopping can be determinedaccording to the embodiments of the present invention, and the DMRSsequence can be generated according to the determined group hoppingpattern, sequence shift pattern, sequence hopping and/or CS hopping. Ifthe VCI is not set by the higher layer, the PUCCH DMRS sequence and/orthe PUSCH DMRS sequence can be generated using a PCI as in aconventional wireless communication system. The above-describedembodiments of the present invention may be independently applied or twoor more embodiments may be simultaneously applied, and redundantdescriptions are avoided for clarity.

The UE may map the generated DMRS sequence to an uplink resource andtransmit the DMRS sequence to the eNB in step S1330. The positions ofREs mapped to the PUSCH DMRS sequence and the positions of REs mapped tothe PUCCH DMRS sequence are as described with reference to FIGS. 5 to10.

When the eNB receives an uplink RS transmitted from the UE, the eNB candetect the uplink RS on the assumption that the UE generates the uplinkRS according to the RS sequence generation scheme proposed by thepresent invention.

FIG. 14 illustrates a configuration of a UE device according to anembodiment of the present invention.

Referring to FIG. 14, a UE device 10 according to an embodiment of thepresent invention may include a transmitter (Tx module) 12, a receiver(Rx module) 11, a processor 13, a memory 14 and a plurality of antennas15. The plurality of antennas 15 means that the UE device supports MIMOtransmission and reception. The transmitter 12 can transmit signals,data and information to an external device (e.g. eNB). The receiver 11can receive signals, data and information from an external device (e.g.eNB). The processor 13 can control the overall operation of the UEdevice 10.

The UE device 10 according to an embodiment of the present invention canbe configured to transmit an uplink signal.

The processor 13 of the UE device 10 can receive a VCI (e.g. n_(ID)^(RS)) using the receiver 11 from an eNB through higher layer signaling(e.g. RRC signaling). Here, a VCI (e.g. n_(ID) ^(PUCCH)) for a PUCCHDMRS and a VCI (e.g. n_(ID) ^(PUSCH)) for a PUSCH DMRS may beindependently signaled/set.

The processor 13 of the UE device 10 can be configured to generate an RSsequence (e.g. a PUCCH DMRS sequence and/or a PUSCH DMRS sequence). Theembodiments of the present invention may be applied to DMRS sequencegeneration. For example, when the VCI is set by a higher layer, theprocessor 13 can determine a group hopping pattern, a sequence shiftpattern, sequence hopping and/or CS hopping according to the embodimentsof the present invention and generate the DMRS sequence according to thedetermined group hopping pattern, sequence shift pattern, sequencehopping and/or CS hopping. Alternatively, a group hopping pattern, asequence shift pattern, sequence hopping and/or CS hopping, which can begenerated for each VCI, can be previously generated as a table andappropriate values can be detected from the table according to a setVCI. If the VCI is not set by the higher layer, the PUCCH DMRS sequenceand/or the PUSCH DMRS sequence may be generated using a PCI as in aconventional wireless communication system.

The processor 13 of the UE device 10 can map the generated DMRS sequenceto an uplink resource and transmit the DMRS sequence to the eNB usingthe transmitter 12. The positions of REs mapped to the PUSCH DMRSsequence and the positions of REs mapped to the PUCCH DMRS sequence areas described with reference to FIGS. 5 to 10.

In addition, the processor 13 of the UE device 10 processes informationreceived by the UE device 10, information to be transmitted to anexternal device, etc. The memory 14 can store the processed informationfor a predetermined time and can be replaced by a component such as abuffer (not shown).

The UE device 10 may be implemented such that the above-describedembodiments of the present invention can be independently applied or twoor more embodiments can be simultaneously applied, and redundantdescriptions are avoided for clarity.

An eNB device 20 according to an embodiment of the present invention caninclude a transmitter (Tx module) 22, a receiver (Rx module) 21, aprocessor 23, a memory 24 and antennas 25. When the processor 23 of theeNB device 20 receives an uplink RS transmitted from the UE device 10,the processor 23 of the eNB device 20 can be configured to detect theuplink RS on the assumption that the UE device 10 generates the uplinkRS according to the RS sequence generation scheme proposed by thepresent invention.

While an eNB is exemplified as a downlink transmission entity or anuplink reception entity and a UE is exemplified as a downlink receptionentity or an uplink transmission entity in the embodiments of thepresent invention, the scope of the present invention is not limitedthereto. For example, description of the eNB can be equally applied to acase in which a cell, an antenna port, an antenna port group, an RRH, atransmission point, a reception point, an access point or a relay nodeserves as an entity of downlink transmission to a UE or an entity ofuplink reception from the UE. Furthermore, the principle of the presentinvention described through the various embodiment of the presentinvention can be equally applied to a case in which a relay node servesas an entity of downlink transmission to a UE or an entity of uplinkreception from the UE or a case in which a relay node serves as anentity of uplink transmission to an eNB or an entity of downlinkreception from the eNB.

The embodiments of the present invention may be implemented by variousmeans, for example, hardware, firmware, software, or combinationsthereof.

When the embodiments of the present invention are implemented usinghardware, the embodiments may be implemented using at least one ofApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

It is obvious to those skilled in the art that claims that are notexplicitly cited in each other in the appended claims may be presentedin combination as an exemplary embodiment of the present invention orincluded as a new claim by subsequent amendment after the application isfiled.

INDUSTRIAL APPLICABILITY

The above-described embodiments of the present invention can be appliedto various mobile communication systems.

What is claimed is:
 1. A method for transmitting, by a user equipment(UE), an uplink reference signal, the method comprising: obtaining, bythe UE, a virtual cell identity n^(PUSCH) _(ID) and a physical cellidentity N^(cell) _(ID); generating, by the UE, a first reference signalfor demodulation of a physical uplink shared channel (PUSCH) based onthe virtual cell identity n^(PUSCH) _(ID); transmitting, by the UE, thefirst reference signal; generating, by the UE, a second reference signalfor demodulation of a physical uplink control channel (PUCCH) based onthe physical cell identity N^(cell) _(ID); and transmitting, by the UE,the second reference signal, wherein the virtual cell identity n^(PUSCH)_(ID)ε{0, . . . , 509}, and the physical layer cell identity N^(cell)_(ID)ε{0, . . . , 503}.
 2. The method according to claim 1, wherein eachof the first and second reference signals is generated using asequence-shift pattern, and wherein a sequence-shift pattern f^(PUSCH)_(SS) for the first reference signal is determined according tof^(PUSCH) _(SS)=n^(PUSCH) _(ID) mod 30, and a sequence shift patternf^(PUSCH) _(SS) for the second reference signal is determined accordingto f^(PUSCH) _(SS)=N^(cell) _(ID) mod
 30. 3. The method according toclaim 2, further comprising: receiving a higher layer signal includingΔ_(ss)ε{0, . . . , 29}, wherein the sequence-shift pattern f_(ss)^(PUSCH) for the first reference signal is determined according tof^(PUSCH) _(SS)=n^(PUSCH) _(ID) mod 30 irrespective of Δ_(ss)ε{0, . . ., 29}.
 4. The method according to claim 1, wherein the virtual cellidentity n^(PUSCH) _(ID) is provided by a higher layer signal.
 5. A userequipment (UE) for transmitting an uplink reference signal, the UEcomprising: a transmitter, and a processor configured to control thereceiver and the transmitter, the processor configured to: obtain avirtual cell identity n^(PUSCH) _(ID) and a physical cell identityN^(cell) _(ID); generate a first reference signal for demodulation of aphysical uplink shared channel (PUSCH) based on the virtual cellidentity n^(PUSCH) _(ID); control the transmitter to transmit the firstreference signal; generate a second reference signal for demodulation ofa physical uplink control channel (PUCCH) based on the physical cellidentity N^(cell) _(ID); and control the transmitter to transmit thesecond reference signal, wherein the virtual cell identity n^(PUSCH)_(ID)ε{0, . . . , 509}, and the physical layer cell identity N^(cell)_(ID)ε{0, . . . , 503}.
 6. The UE according to claim 5, wherein each ofthe first and second reference signals is generated using asequence-shift pattern, and wherein a sequence-shift pattern f^(PUSCH)_(SS) for the first reference signal is determined according tof^(PUSCH) _(SS)=n^(PUSCH) _(ID) mod 30, and a sequence shift patternf^(PUSCH) _(SS) for the second reference signal is determined accordingto f^(PUSCH) _(SS)=N^(cell) _(ID) mod
 30. 7. The UE according to claim6, wherein the processor controls the transmitter to receive a higherlayer signal including Δ_(ss)ε{0, . . . , 29}, and wherein the sequenceshift pattern f_(ss) ^(PUSCH) for the first reference signal isdetermined according to f^(PUSCH) _(SS)=n^(PUSCH) _(ID) mod 30irrespective of Δ_(ss)ε{0, . . . , 29} provided by a higher layersignal.
 8. The UE according to claim 5, wherein the virtual cellidentity n^(PUSCH) _(ID) is provided by a higher layer signal.